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應(yīng)助: 1 (幼兒園)
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蟲號: 3458828
注冊: 2014-10-07
性別: MM
專業(yè): 中藥學(xué)其他科學(xué)問題

[求助] 幫忙翻譯一下這個合成實驗步驟

Synthesis of Ginkgotoxine-5'-Glucoside
   Acetic anhydride (0.8 mL) was added dropwise to a solution of ginkgotoxin
(1.90 g), triethylamine (1.6 mL), and dimethylaminopyridine (0.38 g) in
dichloromethane (60 mL), under ice-cooling. The mixture was stirred under
ice-cooling for 20 min, and then the solvent was evaporated in vacuo. The
residue was diluted with saturated sodium hydrogen carbonate and extracted
with ethyl acetate. The organic layer was washed with saturated sodium
hydrogen carbonate and dried over anhydrous sodium sulfate. After evaporation
of the solvent, the crude product was purified by column chromatography
on silica gel, using chloroform/methanol (50/1, v/v) as an eluent,
to give 3-acetoxy-5-hydroxymethyl-4-methoxymethyl-2-methylpyridine
(ginkgotoxin-3-acetate) (1.16 g) as a pale yellow oily product. IR
(neat):3300 (OH), 1775 (C55O). 1H-NMR (CDCl3):2.34 (3H, s, CH3CO-),
2.36 (3H, s, 2-CH3), 3.33 (3H, s, 4-CH2OCH3), 4.45 (2H, s, 4-CH2OCH3),
4.64 (2H, s, 5-CH2OH), 8.31 (1H, s, 6-H).
      A mixture of ginkgotoxin-3-acetate (1.82 g), 2, 3, 4, 6-tetra-O-acetyl-a-
D-glucopyranosyl bromide (3.99 g),[12] silver carbonate (2.68 g), and
Molecular Sieves 3A (14 g) in dry dichloromethane (50 mL) was refluxed
for 3 days in the dark. After removal of insoluble materials by filtration,
the solvent was evaporated in vacuo. The crude product was purified by
column chromatography on silica gel using benzene/acetone (5/1) and recrystallization from ethyl acetate/hexane, to give ginkgotoxin-50-glucoside
pentaacetate (2.0 g) as colorless prisms. mp: 126–1278C. IR (nujol):1750
(C55O). 1H-NMR (CDCl3):1.96, 1.98, 1.99, 2.08, 2.33 (each 3H, s, CH3CO-),
2.39 (3H, s, 2-CH3), 3.26 (3H, s, 4-CH2OCH3), 3.67 (1H, ddd, J ¼ 2.3, 4.6,
10.0 Hz, Glc H-5), 4.14 (1H, dd, J ¼ 2.3, 12.0 Hz, Glc H-6), 4.24 (1H, dd,
J ¼ 4.6, 12.0 Hz, Glc H-6), 4.36, 4.40 (2H, AB, J ¼ 12.0 Hz, 4-CH2O-),
4.54 (1H, d, J ¼ 8.0 Hz, Glc H-1), 4.69, 4.97 (2H, AB, J ¼ 12.6 Hz,
5-CH2O-), 4.98-5.09 (3H, m, Glc H-2, H-3, H-4), 8.31 (1H, s, 6-OH).
   Potassium hydroxide, 2M(2 mL) was added to a solution of ginkgotoxin-
50-glucoside pentaacetate (222 mg) in methanol (4 mL). The mixture was
stirred at room temperature overnight in the dark. The pH was adjusted to
8–9 with acetic acid, and the solvent was evaporated in vacuo. The residue
was dissolved in a minimal amount of water and was applied to a reversedphase
column (240 15 mm) equilibrated with water. After washing the
column with water, elution was accomplished with 3% methanol. The
eluate was lyophilized to give ginkgotoxin- 50-glucoside as white crystals
(115 mg). mp: 128–1338C. IR (nujol):3400 (OH). 1H-NMR (D2O-DMSOd6):
2.32 (3H, s, 2-CH3), 2.92-3.11 (4H, m, Glc H-2, H-3, H-4, H-5), 3.23
(3H, s, 4-CH2OCH3), 3.42 (1H, dd, J ¼ 5.7, 11.7 Hz, Glc H-6), 3.65 (1H,
dd, J ¼ 1.7, 11.7 Hz, Glc H-6), 4.13 (1H, d, J ¼ 7.4 Hz, Glc H-1), 4.52, 4.55
(2H, AB, J ¼ 11.4 Hz, 4-CH2O-), 4.54, 4.78 (2H, AB, J ¼ 12.0 Hz, 5-CH2O-),
7.92 (1H, s, 6-H). UV lmax (5mM potassium phosphate, pH 2.5) nm:291.
ESI-MS m/z:346 [M þ H]þ.

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